Tumor radiosensitization and /or chemopotentiation using isocoumarin derivatives

ABSTRACT

A method for enhancing the efficacy of chemotherapy and/or radiation in the treatment of cancer in animals, particularly humans, is provided wherein certain isocoumarin derivatives which exhibit unique radiosensitization activity and/or chemopotentiation properties are employed in a combination treatment with ionizing radiation and/or chemotherapy.

[0001] This application claims priority to U.S. application Ser. No. 09/794,417, filed Feb. 27, 2001 and U.S. Provisional Application No. 60/186,071, filed Feb. 29, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to isocoumarin derivatives and their use in cancer therapy. More particularly, it relates to the use of isocoumarin derivatives in the prevention or treatment of cancer by inhibiting tumor neovascularization, or angiogenesis, in combination with enhancing tumor sensitivity to radiation therapy and/or chemotherapy.

[0004] 2. Description of Related Art

[0005] Normal tissue homeostasis is achieved by an intricate balance between the rate of cell proliferation and cell death. Disruption of this balance either by increasing the rate of cell proliferation or decreasing the rate of cell death can result in the abnormal growth of cells and is thought to be a major event in the development of cancer. The effects of cancer are catastrophic, causing over half a million deaths per year in the United States alone. Conventional strategies for the treatment of cancer include chemotherapy, radiotherapy, surgery, biological therapy or combinations thereof. However, further advances in these strategies are limited by lack of specificity and excessive toxicity to normal tissues. In addition, certain cancers are refractory to treatments such as chemotherapy, and some of these strategies, such as surgery, are not always viable alternatives.

[0006] Once the diagnosis of cancer is established, the most urgent question is whether the disease is localized or has spread to lymph nodes and distant organs. The most fearsome aspect of cancer is metastasis, and this fear is well justified. In nearly 50% of patients, surgical excision of primary neoplasms is ineffective, because metastasis has occurred by the time the tumor is large enough for resection (Sugarbaker, 1979; Fidler and Balch, 1987). Metastases can be located in different organs and in different regions of the same organ, making complete eradication by surgery, radiation, drugs or biotherapy difficult. Furthermore, the organ microenvironment significantly influences the response of tumor cells to therapy (Fidler, 1985), as well as the efficiency of anticancer drugs, which must be delivered to tumor foci in amounts sufficient to destroy cells without causing undesirable side effects (Fidler and Poste, 1985). In addition, the treatment of metastatic cancer is greatly hindered due to the biological heterogeneity of cancer cells, and the rapid emergence of tumor cells that become resistant to most conventional anticancer agents (Fidler and Poste, 1985).

[0007] One of the processes involved in the growth of both primary and secondary (metastatic) tumors is neovascularization, or creation of new blood vessels which grow into the tumor. This neovascularization is termed angiogenesis (Folkman, 1986; Folkman, 1989), which provides the growing tumor with a blood supply and essential nutrients. Although tumors of 1-2 mm in diameter can receive all nutrients by diffusion, further growth depends on the development of an adequate blood supply through angiogenesis. Inhibition of angiogenesis provides a novel and more general approach for treating metastases by manipulation of the host environment.

[0008] Several angiogenic molecules released by both tumor endothelial cells and the normal cells surrounding the tumor endothelial cells mediate the induction of angiogenesis. The prevascular stage of a tumor is associated with local benign tumors, whereas the vascular stage is associated with tumors capable of metastasizing. Moreover, studies using light microscopy and immunohistochemistry concluded that the number and density of microvessels in different human cancers directly correlate with their potential to invade and produce metastasis (Weidner, et al., 1991; Weidner, et al., 1993). Not all angiogenic tumors produce metastases, but the inhibition of angiogenesis prevents the growth of tumor endothelial cells at both the primary and secondary sites and thus can prevent the emergence of metastases.

[0009] Both controlled and uncontrolled angiogenesis are thought to proceed in a similar manner. Endothelial cells and pericytes, surrounded by a basement membrane, form capillary blood vessels. Angiogenesis begins with the erosion of the basement membrane by enzymes released by endothelial cells and leukocytes. The endothelial cells, which line the lumen of blood vessels, then protrude through the basement membrane. Angiogenic stimulants induce the endothelial cells to migrate through the eroded basement membrane. The migrating cells form a “sprout” off the parent blood vessel, where the endothelial cells undergo mitosis and proliferate. The endothelial sprouts merge with each other to form capillary loops, creating the new blood vessel.

[0010] Persistent and unregulated angiogenesis is characteristic of tumor growth and it supports the pathological damage seen in cancer. Thus, tumor growth is an angiogenesis-dependent process (Folkman, 1971). After an initial prevascular phase, every increase in tumor endothelial cell population is preceded by an increase in new capillaries converging on the tumor. Expansion of tumor volume beyond this phase requires the induction of new capillary blood vessels.

[0011] Blockade of the angiogenic process has emerged as an important anticancer strategy. It has been demonstrated that in mice bearing subcutaneous Lewis lung carcinomas (3LL), the primary or local tumor releases an angiogenesis-inhibiting substance, named angiostatin (O'Reilly, et al., 1994). Angiostatin is a 38-kDa fragment of plasminogen that selectively inhibits proliferation of endothelial cells. Angiostatin has been shown to suppress vascularization and, hence, growth of metastases when used as an adjuvant to conventional therapy (e.g. see, U.S. Pat. No. 5,733,876). Several studies have produced results consistent with this model. After systemic administration, purified angiostatin can produce apoptosis in metastases (Holmgren, et al., 1995) and sustain dormancy of several human tumors implanted subcutaneously in nude mice (O'Reilly et al., 1996).

[0012] Clearly, angiogenesis plays a major role in tumor development and maintenance. As stated earlier, conventional cancer therapeutic regimens are hampered by the ability of the cancer cell to adapt and become resistant to the therapeutic modality used to combat tumor growth. Certain isocoumarin derivatives are known to have an inhibiting effect on vascularization (e.g. see, U.S. Pat. No. 6,020,363 which is incorporated herein by reference), and it is likely that such isocoumarin derivatives will be useful in reducing the growth, size, spreading, and otherwise mitigating the deleterious effect of a tumor by virtue of their angiogenesis-inhibiting properties. Significantly, pursuant to the present invention, isocoumarin derivative treatment has also been shown to sensitize endothelial cells and established tumors to the cytotoxic effects of ionizing radiation and/or conventional chemotherapy. Thus, the combination of these properties of isocoumarin derivatives provides for a promising cancer therapeutic strategy and establishes a novel medical application for these drugs.

[0013] An isocoumarin derivative, particularly 3-hydroxymethyl-6-methoxy-8-hydroxy-1H-2-benzopyran-1-one, subsequently named cytogenin (formula I, below), was first identified as a compound produced by the M143-37F11 strain of Streptoverticillium eurocidicum. Cytogenin has attracted attention under the name of the antibiotic M143-37F11 because of its growth-inhibiting activity against various animal cells and human cancer cells (Japanese Patent Laid-Open No. 2177/'91). Cytogenin given by oral administration demonstrated antitumor activities against several transplantable mouse solid tumors. However, this compound showed very low anti-proliferation inhibitory activity against cultured tumor cells and low toxicity in mice and dogs. The mechanism of action of antitumor activity of cytogenin was found to be associated with its ability to disrupt the neovascularization in growing tumors. While cytogenin demonstrated promise as an antitumor agent, its in vivo instability rendered it unfit for clinical development. Investigations of chemical derivatives of cytogenin identified a highly stable analog, herein referred to as NM-3 (formula II, below) that retained the important biological properties of the parent compound. NM-3 is the most extensively studied member of this class of compounds (e.g. see, U.S. Pat. No. 6,020,363), and will serve as the primary example of an isocoumarin derivative useful in the treatment methods of the present invention.

3. SUMMARY OF INVENTION

[0014] In its broadest aspects, the present invention is directed to the use of isocoumarin derivatives of formula III, below, in combination with ionizing radiation and/or chemotherapeutic agents in the treatment of cancer to provide a therapeutic effect, in terms of reduced cancer mass or metastatic potential, which is enhanced over that obtained with radiation and/or the chemotherapeutic agent alone.

[0015] The isocoumarin derivatives useful in the methods of the invention include compounds of formula III:

[0016] wherein each of X¹, X², and X³ may independently be sulphur or oxygen; and X⁴ is sulfur, oxygen or —NH—; R¹ is hydrogen or C₁₋₆ alkyl, and R² and R³ may be the same or different and each represents C₁₋₆ alkyl, C₇₋₁₀ alkaryl, hydroxy or hydrogen, and n is zero or a whole integer of from 1 to 3. The isocoumarin derivatives of the formula III function as radiation sensitizers and/or chemopotentiators, providing therapeutic benefit in the treatment of cancer which is additive or synergistic over that obtained with the isocoumarin derivative on the one hand, or ionizing radiation on the chemotherapeutic agent on the other hand, when either is used as the single treatment modality.

[0017] Accordingly, the present invention provides a method of inhibiting the growth of a tumor cell comprising contacting said tumor cell with an isocoumarin derivative of formula III, above, and a second growth inhibiting modality (or mode of treatment) selected from a dose of ionizing radiation or a chemotherapeutic agent or combination of said radiation and chemotherapeutic agent, wherein the does of said isocoumarin derivative, when combined with the second growth inhibiting modality, is effective to inhibit growth of said tumor cell.

[0018] In one embodiment, the invention further provides a method of treating cancer in a human patient comprising administering an isocoumarin derivative of formula III, above, to a human patient together with a dose of ionizing radiation and/or a chemotherapeutic agent, wherein the dose of said isocoumarin derivative, when combined with the dose of ionizing radiation and/or chemotherapeutic agent, is effective to treat the cancer. In this embodiment the cancer subject to treatment is suitably selected from the group consisting of skin cancer, prostate cancer, lung cancer, brain cancer, breast cancer, ovarian cancer, cervical cancer, liver cancer, pancreatic cancer, colon cancer, stomach cancer, lymphoma and leukemia. In the method of the invention, the isocoumarin derivatives are suitably administered prior to, or simultaneously with, the ionizing radiation and/or chemotherapeutic agent. The invention further provides a method of potentiating the effect of ionizing radiation on a tumor cell comprising contacting the tumor cell with an isocoumarin derivative of formula III, above, and then contacting the tumor cell with ionizing radiation, as well as a method of sensitizing a tumor cell to the growth inhibiting or cell killing effects of a chemotherapeutic agent, comprising contacting the tumor cell with an isocoumarin derivative of formula III, above, and then contacting the tumor cell with the chemotherapeutic agent.

[0019] Further, as used herein, chemotherapeutic agent includes all conventional cytotoxic and cytostatic agents used in cancer treatment and prevention including, from a mechanism of action standpoint; Tubulin interactive agents, DNA-interactive agents, antimetabolites and antifolates, antihormonals, antibiotics, antivirals, ODC inhibitors, and other cytotoxic agents, and prodrugs.

4. BRIEF DESCRIPTION OF THE DRAWINGS

[0020]FIG. 1. is a series of three graphs showing the effects of a constant amount of gamma radiation combined with various concentrations of NM-3, angiostatin and endostatin on the number of human umbilical vein endothelial cell (HUVEC) colonies formed following treatment;

[0021]FIG. 2. is a graph showing the effects of gamma radiation and the combination of gamma radiation and NM-3 on the number of human umbilical vein endothelial cell (HUVEC) colonies formed following treatment;

[0022]FIG. 3 is a series of three graphs showing the effects of gamma radiation combined with either NM-3, angiostatin or endostatin on Lewis Lung Carcinoma tumor growth in C57B46 mouse xenographs.

[0023]FIG. 4. is a graph showing the tumor growth inhibitory effect of NM-3 alone, and in combination with Paclitaxel on 50 mm³ pre-existing MDAAMB435 human breast tumor xenografts in a nude mouse model system;

[0024]FIG. 5. is a graph showing the tumor growth inhibitory effect of NM-3 alone, and in combination with Paclitaxel on 100 mm³ pre-existing MDAAMB435 human breast tumor xenografts in a nude mouse model system;

[0025]FIG. 6. is a graph showing the effect of different dosing regimens of NM-3 on the tumor growth inhibitory effect of NM-3 against 100 mm³ pre-existing MDAAMB435 human breast tumor xenografts in a nude mouse model system;

[0026]FIG. 7. is a graph showing the tumor growth inhibitory effect of NM-3 alone, and in combination with 5-fluorouracil (5-FU) on 50 mm³ pre-existing MDAAMB435 human breast tumor xenografts in a nude mouse model system;

[0027]FIG. 8. is a graph showing the effect of NM-3, radiation and the combination on established Lewis Lung Carcinoma tumors in a murine model system;

[0028]FIG. 9. is a graph showing the effect of NM-3, radiation and the combination of the growth of Seq-1 tumors a nude mouse model.

5. DETAILED DESCRIPTION OF INVENTION

[0029] The present invention provides methods of enhancing the efficacy of conventional chemotherapy and/or radiation in the treatment of cancer in animals, particularly humans harboring such cancer, through the use of a class of isocoumarin derivatives, which exhibit unique radiosensitization activity and/or chemopotentiation properties when employed in combination with chemotherapeutic agents and/or radiation. Using the isocoumarin derivatives of the present invention in combination with conventional chemotherapy and/or radiation is anticipated to facilitate not only greater efficacy in the tumor cell killing and growth inhibition effects of the treatment, but also to afford treatment regimes which present less toxicity and/or adverse side effects to the treatment subjects, since the dosage and/or intensity of the treatment can be reduced as a result of the treatment enhancing effects of the isocoumarin derivatives.

[0030] A. Isocoumarin Derivatives

[0031] The isocoumarin derivatives of formula III, above, which are useful in the invention preferably include those wherein X¹, X² and X³ are oxygen; X⁴ is oxygen or sulfur; R¹ is C₁₋₃ alkyl; R² and R³ are hydrogen or C₁₋₆ alkyl and n is 0, 1 or 2, or a pharmaceutically acceptable salt thereof. Suitable isocoumarin and thiaisocoumarin derivatives in this preferred embodiment include:

[0032] 2-(8-hydroxy-6-methoxy-1-oxo-1H-2-benzopyran-3-y 1) acetic acid

[0033] 2-(8-hydroxy-6-ethoxy-1-oxo-1H-2-benzopyran-3-y 1) propionic acid

[0034] 2-(8-hydroxy-6-methoxy-1-oxo-1H-2-benzothiopyran-3-yl) acetic acid

[0035] 2-(8-hydroxy-6-ethoxy-1-oxo-1H-2-benzothiopyran-3-y 1) acetic acid

[0036] 2-(8-hydroxy-6-methoxy-1-oxo-1H-2-benzopyran-3-y 1) propionic acid

[0037] 2-(8-hydroxy-6-methoxy-1-oxo-1H-2-benzothiopyran-3-y 1) propionic acid

[0038] In a more preferred embodiment, the isocoumarin derivatives employed in the methods of the invention have a chemical structure in accordance with formula IV, below.

[0039] Wherein R¹ is C₁₋₃ alkyl, and R² and R³ may be the same or different and each represents a hydrogen atom or C₁₋₆ alkyl and n is 0 or 1. Most preferably, R¹ is methyl, R² is hydrogen and R³ is methyl with n being the whole integer 1. This most preferred isocoumarin is set forth in formula II, above, and is hereinafter referred to as NM-3.

[0040] The isocoumarin derivatives which are useful in the methods of the present invention, may be prepared from conventional starting materials using a variety of synthetic methods described in the prior art, including the synthesis methods set forth in U.S. Pat. Nos. 6,020,363; 3,975,535; 3,960,892; German Patent No. DE2448387; publications “A new and concise synthesis of 3-aryl-and 3-alkyl-1H-2-benzothiopyran-1-ones (thioisocoumarin),” Couture, Axel, et al., Synthesis (1990) (12), 1133-4; “Pharmaceutical compositions and methods of treatment with 1-oxo-1H-2-benzothiopran-3-carboxylic acid derivatives,” Bare, Thomas M., et al. (Richard-Merrell, Inc. USA) (1977), 4 pp., Division of U.S. Pat. No. 3,690,892; “Vinyl azides in heterocyclic synthesis. Part 9. Synthesis of the isoquinolone alkaloid siamine by intramolecular aza-wittig reaction,” Kennedy, Michael, et al., London, UK, J. Chem. Soc., Perkin Trans. 1 (1987), (6), 1395-8; Bringmann et al, J. Organomet. Chem., [472] 275-284 (1994); Bringmann et al, Z. Naturforsch. B [52] 355-358 (1997); Letcher et al, J. Chem. Soc. Perk. Trans. 1 [10] 1715-1720 (1998); Dijksman and Newbold, J. Chem. Soc., 1213, 1216 (1951); Kiang and Mann, J. Chem. Soc., 1909, 1914 (1951); Couture et al, Synthesis [12] 1133-1134 (1990); Woodroofe et al, J. Chem. Soc. Perk. Trans. 2 [1] 55-60 (2000); Padwa et al, J. Org. Chem. [64] 3595-3607 (1999); Norisuke, Bull. Chem. Soc. Japan [58] 1088-1093 (1985); Spassov et al, Magn. Res. Chem. [23] 795-799 (1985); Hata and Atsushi, Chem. Lett., 309-312 (1983); Yousif et al, Chem. Pharm. Bull [30] 1680-1691 (1982); Singh et al, Synthesis [10] 791-793 (1983); and Sakamoto et al, Chem. Pharm. Bull. [33] 626-633 (1985) all of which are incorporated herein by reference. The techniques set forth in U.S. Pat. No. 6,020,363 are particularly useful in its synthesis of the preferred isocoumarin in accordance with this invention, including NM-3, whereas the synthetic methodology set forth in U.S. Pat. No. 3,975,535 is useful for the broader class of isocoumarin derivatives employed in the invention, including the thiaisocoumarin analogs.

[0041] The isocoumarin derivatives employed in the methods of the invention can be formulated in a variety of conventional pharmaceutical formulations and administered to cancer patients, in need of treatment, by any one of the drug administration routes conventionally employed including oral, intravenous, intraarterial, parental or intrapenitoneal. In this invention, the preferred routes of administration include intravenous (IV), intraperitoneal (IP) and oral, with oral administration being most preferred, to take advantage of the high level of oral bioavailability exhibited by NM-3 and other isocoumarin derivatives according to the invention.

[0042] For oral administration the isocoumarin derivatives of the invention may be formulated, for example, with an inert dilutent or with an assimiable edible carrier, or enclosed in hard or soft shell gelatin capsules, or compressed into tablets, or incorporated directly with the food of the diet. For oral therapeutic administration, the active compound may be incorporated with excipients and used in the form of ingestible tablets, buccal tablets, troches, capsules, elixirs, suspensions, syrups, wafers, and the like. Such compositions and preparations may, of course, be varied and may conveniently be between about 2 to about 60% of the weight of the unit. The amount of active compounds in such therapeutically useful compositions is such that a suitable dosage will be obtained.

[0043] The tablets, troches, pills, capsules and the like may also contain the following: a binder, a gum tragacanth, acacia, cornstarch, or gelatin; excipients, such as dicalcium phosphate; a disintegrating agent, such as corn starch, potato starch, alginic acid and the like; a lubricant, such as magnesium stearate; and a sweetening agent, such as sucrose, lactose or saccharin may be added or a flavoring agent, such as peppermint, oil of wintergreen, or cherry flavoring. When the dosage unit for is a capsule, it may contain, in addition to materials of the above type, a liquid carrier. Various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit. For instance, tablets, pills, or capsules may be coated with shellac, sugar or both. A syrup or elixir may contain the active compounds sucrose as a sweetening agent methyl and propylparabens as preservatives, a dye and flavoring, such as cherry or orange flavor. Of course, any material used in preparing a dosage unit form should be pharmaceutically pure and substantially non-toxic in the amounts employed. In addition, other chemotherapeutic compounds may be incorporated into sustained-release preparation and formulations.

[0044] Pharmaceutical formulations of the isocoumarin derivatives in accordance with the invention which are suitable for injectable use include sterile aqueous solutions or dispersions and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions. In all cases the form must be sterile and must be fluid to the extent that each syringability exists. It must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms, such as bacteria and fungi. The carrier can be a solvent or dispersion medium containing, for example, by the use of a coating, such as lecithin, by the maintenance of the required particle size in the case of dispersion and by the use of surfactants. The prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents, for example, parabens, chlorobutanol, phenol, sorbic acid, thimerosal, and the like. In many cases, it will be preferable to include isotonic agents, for example, sugars or sodium chloride. Prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption, for example, aluminum monostearate and gelatin.

[0045] Sterile injectable solutions are prepared by incorporating the active isocoumarin compounds in the required amount in the appropriate solvent with various of the other ingredients enumerated above, as required, followed by filtered sterilization. Generally, dispersions are prepared by incorporating the various sterilized active ingredients into a sterile vehicle which contains the basic dispersion medium and the required other ingredients from those enumerated above. In the case of sterile powders for the preparation of sterile injectable solutions, the preferred methods of preparation are vacuum-drying and freeze-drying techniques which yield a powder of the active ingredient plus any additional desired ingredient from a previously sterile-filtered solution thereof.

[0046] As used herein, “pharmaceutically acceptable carrier” includes any and all solvents, dispersion media, coatings, antibacterial and antifungal agents, isotonic and absorption delaying agents and the like. The use of such media and agents for pharmaceutical active substances is well known in the art. Except insofar as any conventional media or agent is incompatible with the active ingredient, its use in the therapeutic compositions is contemplated. Supplementary active ingredients can also be incorporated into the composition.

[0047] B. Chemotherapeutic Agents

[0048] The chemotherapeutic agents useful in the methods of the invention include the full spectrum of compositions and compounds which are known to be active in killing and/or inhibiting the growth of cancer cells. The chemotherapeutic agents, grouped by mechanism of action include DNA-interactive agents, antimetabolites, Tubulin interactive agents, antihormonals, anti-virals, ODC inhibitors and other cytotoxics such as hydroxy-urea. Any of these agents are suitable for use in the methods of the present invention.

[0049] DNA-interactive agents include the alkylating agents, e.g., Cisplatin, Cyclophosphamide, Altretamine; the DNA strand-breakage agents, such as Bleomycin; the intercalating topoisomerase II inhibitors, e.g., Dactinomycin and Doxorubicin); the nonintercalating topoisomerase II inhibitors such as, Etoposide and Teniposide; and the DNA minor groove binder Plicamycin.

[0050] The alkylating agents form covalent chemical adducts with cellular DNA, RNA and protein molecules and with smaller amino acids, glutathione and similar chemicals. Generally, these alkylating agents react with a nucleophilic atom in a cellular constituent, such as an amino, carboxyl, phosphate, sulfhydryl group in nucleic acids, proteins, amino acids, or glutathione. The mechanism and the role of these alkylating agents in cancer therapy is not well understood. Typical alkylating agents include: nitrogen mustards, such as Chlorambucil, Cyclophosphamide, Isofamide, Mechlorethamine, Melphalan, Uracil Mustard; aziridine such as Thiotepa; methanesulphonate esters such as Busulfan; nitroso ureas, such as Carmustine, Lomustine, Streptozocin; platinum complexes such as Cisplatin, Carboplatin; bioreductive alkylators, such as Mitomycin and Procarbazine, Dacarbazine and Altretemine; DNA strand-breaking agents including Bleomycin. Topoisomerases are ubiquitous cellular enzymes which initiate transient DNA strand breaks during replication to allow for free rotation of the strands. The functionality of these enzymes is critical to the replication process of DNA. Without them, the torsional strain in the DNA helix prohibits free rotation, the DNA strands are unable to separate properly, and the cell eventually dies without dividing. Topo I links to the 3′-terminus of a DNA single strand break, while Topo II links to the 5′-terminus of a double strand DNA break. DNA topoisomerase II inhibitors include the following: intercalators such as Amsacrine, Dactinomycin, Daunorubicin, Doxorubicin, Idarubicin and Mitoxantrone; nonintercalators such as Etoposide and Teniposide; camtothecins including Irinotecam (CDT-II) and Topotecan. A representative DNA minor groove binder is Plicamycin.

[0051] The antimetabolites generally exert cytotoxic activity by interfering with the production of nucleic acids by one or the other of two major mechanisms. Some of the drugs inhibit production of the deoxyribonucleoside triphosphates that are the immediate precursours of DNA synthesis, thus inhibiting DNA replication. Some of the compounds are sufficiently like purines or pyrimidines to be able to substitute for them in the anabolic nucleotide pathways. These analogs can then be substituted into the DNA and RNA instead of their normal counterparts. The antimetabolites useful herein include: folate antagonists such as Methotrexate and Trimetrexate; pyrimidine antagonists such as Fluorouracil, Fluorodeoxyuridine, Azacitidine, Cytarabine, and Floxuridine; purine antagonists include Mercaptopurine, 6-thioguanine, Fludarabine, Pentostatin; sugar modified analogs include Cytarabine, Fludarabine; ribonucleotide reductase inhibitors include Hydroxyurea.

[0052] Tubulin interactive agents interfere with cell division by binding to specific sites on Tubulin, a protein that polymerizes to form cellular microtubules. Microtubules are critical cell structure units. When the interactive agents bind on the protein, the cell cannot properly form microtubules. Tubulin interactive agents include Vincristine and Vinblastine, both alkaloids and the Taxanes (Paclitaxel and Docetaxel).

[0053] Although their mechanisms of action are different, both taxanes and Vinca Alkaloids exert their biological effects on the cell microtubles. Taxanes act to promote the polymerization of Tubulin, a protein subunit of spindle microtubles. The end result is the inhibition of depolymerization of the microtubles, which causes the formation of stable and nonfunctional microtubles. This disrupts the dynamic equilibrium within the microtuble system, and arrests the cell cycle in the late G₂ and M phases, which inhibits cell replication.

[0054] Like taxanes, Vinca Alkaloids also act to affect the microtuble system within the cells. In contrast to taxanes, Vinca Alkaloids bind to Tubulin and inhibit or prevent the polymerization of Tubulin subunits into microtubles. Vinca Alkaloids also induce the depolymerization of microtubles, which inhibits microtuble assembly and mediates cellular metaphase arrest. Vinca alkaloids also exert effects on nucleic acid and protein synthesis; amino acid, cyclic AMP, and glutathione synthesis; cellular respiration; and exert immunosuppressive activity at higher concentrations.

[0055] Antihormonal agents exert cytotoxic activity by blocking hormone action at the end-receptor organ. Several different types of neoplasm require hormonal stimulation to propogate cell reproduction. The antihormonal agents, by blocking hormone action, deprive the neoplastic cells of a necessary stimulus to reproduce. As the cells reach the end of their life cycle, they die normally, without dividing and producing additional malignant cells. Antihormonal agents are typically derived from natural sources and include: Estrogens, Conjugated Estrogens and Ethinyl Estradiol and Diethylstibesterol, Chlortrianisen and Idenestrol; progestins such as Hydroxyprogesterone Caproate, Medroxyprogesterone, and Megestrol; androgens such as Testosterone, Testosterone Propionate; Fluoxymesterone, Methyltestosterone.

[0056] Adrenal corticosteroids are derived from natural adrenal cortisol or hydrocortisone. They are used because of their anti-inflammatory benefits as well as the ability of some to inhibit mitotic divisions and to halt DNA synthesis. These compounds include Prednisone, Dexamethasone, Methylprednisolone, and Prednisolone.

[0057] Leutinizing-releasing hormone agents or gonadotropin-releasing hormone antagonists are used primarily in the treatment of prostate cancer. These include Leuprolide Acetate and Goserelin Acetate. They prevent the biosynthesis of steroids in the testes.

[0058] Anti-hormonal antigens include antiestrogenic agents such as Tamoxifen, Antiandrogen agents such as Flutamide, and Antiadrenal agents such as Mitotane and Aminoglutethimide.

[0059] ODC (or ornithine decarboxylase) inhibitors inhibit cancerous and pre-cancerous cell proliferation by depleting or otherwise interfering with the activity of ODC, the rate limiting enzyme of polyamine biosynthesis important to neoplastic cell growth. In particular, polyamine biosynthesis wherein ornithine is converted to the polyamine, putrescine, with putrescine being subsequently by converted to spermidine and spermine appears to be an essential biochemical event in the proliferation of neoplastic growth in a variety of cancers and cancer cell lines and the inhibition of ODC activity or depletion of ODC in such neoplastic cells has been shown to reduce polyamine levels in such cells leading to cell growth arrest; more differentiated cell morphology and even cellular senescence and death. In this regard, ODC or polyamine synthesis inhibitors are considered to be more cytotoxic agents functioning to prevent cancer reoccurrence or the conversion of pre-cancerous cells to cancerous cells than cytotoxic or cell killing agents. A suitable ODC inhibitor is eflornithine or a-difluoromethyl-ornithine, an orally available, irreversible ODC inhibitor, as well as a variety of polyamine analogs which are in various stages of pre-clinical and clinical research.

[0060] Other cytotoxics include agents which interfere or block various cellular processes essential for maintenance of cellular functions or cell mitosis as well as agents which promote apoptosis. In this regard, hydroxyurea appears to act via inhibitors of the enzyme ribonucleotide reductase whereas asparaginase enzymatically converts asparagine into non-functional aspartic acid thereby blocking protein synthesis in a tumor.

[0061] Chemotherapeutic agents which are particularly useful in the combination treatment according to the invention include Tubulin interactive agents such as Paclitaxel and Docetaxel; DNA interactive agents such as Cyclophosphamide, Chlorambucil, Cisplatin and Doxorubicin; and antimetabolites such as 5-Fluorouracil and Methotrexate. Preferred chemotherapeutic agents for use in the combination treatment of the invention include Paclitaxel and Cyclophosphamide. When used in the treatment methods of the present invention, it is contemplated that the chemotherapeutic agent of choice can be conveniently used in any formulation which is currently commercially available, and at dosages which fall below or within the approved label usage for single agent use, it being understood that in the combination treatment according to the invention, the effectiveness of the chemotherapeutic agent is enhanced, allowing for corresponding lower dosages.

[0062] C. Ionizing Radiation

[0063] In the present invention, the term “ionizing radiation” means radiation comprising particles or photons that have sufficient energy or can produce sufficient energy via nuclear interactions to produce ionization (gain or loss of electrons). An exemplary and preferred ionizing radiation is an x-radiation. Means for delivering x-radiation to a target tissue or cell are well known in the art. The amount of ionizing radiation needed in a given cell generally depends on the nature of that cell. Means for determining an effective amount of radiation are well known in the art. Used herein, the term “an effective dose” of ionizing radiation means a dose of ionizing radiation that produces an increase in cell damage or death when given in conjunction with the isocoumarin derivatives of the invention, optionally further combined with a chemotherapeutic agent.

[0064] Dosage ranges for x-rays range from daily doses of 50 to 200 roentgens for prolonged periods of time (3 to 4 weeks), to single doses of 2000 to 6000 roentgens. Dosage ranges for radioisotopes vary widely, and depend on the half-life of the isotope, the strength and type of radiation emitted, and the uptake by the neoplastic cells.

[0065] Any suitable means for delivering radiation to a tissue may be employed in the present invention, in addition to external means. For example, radiation may be delivered by first providing a radiolabeled antibody that immunoreacts with an antigen of the tumor, followed by delivering an effective amount of the radiolabeled antibody to the tumor. In addition, radioisotopes may be used to deliver ionizing radiation to a tissue or cell.

[0066] D. Treatment Methods

[0067] Tumors that can be suitably treated with the methods of the present invention include; but are not limited to, tumors of the brain (glioblastomas, medulloblastoma, astrocytoma, oligodendroglioma, ependymomas), lung, liver, spleen, kidney, lymph node, small intestine, pancreas, blood cells, colon, stomach, breast, endometrium, prostate, testicle, ovary, skin, head and neck, esophagus, bone marrow, blood and other tissue. The tumor may be distinguished as metastatic and non-metastatic.

[0068] The treatment with the isocoumarin derivatives may precede or follow irradiation and/or chemotherapy by intervals ranging from seconds to weeks and/or be administered concurrently with such treatments. In embodiments where the isocoumarin derivative and irradiation and/or chemotherapy are applied separately to the cell, steps should be taken to ensure that a significant period of time does not expire between the time of each delivery, such that the combination of the two or three treatments would still be able to exert an advantageously combined effect on the cell. In such instances, it is contemplated that one would contact the cell with the treatment agents or modalities within amount 0.1 to 25 h of each other and, more preferably, within about 1 to 4 h of each other, with a delay time of only about 1 h to about 2 h being most preferred. In some situations, it is desirable to extend the time period of treatment significantly, however, where several days (2, 3, 4, 5, 6 or 7) or several weeks (1, 2, 3, 4, 5, 6, 7 or 8) lapse between the respective administrations. In any case, the invention contemplates that the isocoumarin derivatives may be given before, after or even simultaneously with the ionizing radiation and/or chemotherapeutic agent.

[0069] In one preferred embodiment of the method of the invention, the isocoumarin derivative, for example, NM-3, is administered on a periodic basis (either weekly or daily) for several weeks (at least 3 weeks) prior to administration of either the ionizing radiation or the chemotherapeutic agent. In another embodiment, the extended administration of the isocoumarin derivative can be followed by multiple administrations of radiation doses or doses of the chemotherapeutic agent. Further, if multiple doses of radiation and/or chemotherapy are used on an intermittent basis, the isocoumarin derivative can be administered in the rest periods when no radiation or chemotherapy are being given. It is also anticipated that additional benefit can be achieved by combining the administration of an isocoumarin derivative of the invention with chemotherapy followed by one or more doses of radiation. In this case, the three treatments can be given on a repeated basis with appropriate rest periods until the desired treatment effects are achieved.

[0070] In the methods of the present invention, the actual dosage of isocoumarin derivative employed will depend on a variety of factors including the type and severity of cancer being treated, and the additive or synergistic treatment effects of the isocoumarin derivatives and the other treatment modality or modalities selected. Generally, for the isocoumarin derivatives, a dosage of between about 0.1 milligrams (mg) per kilogram (kg) of body weight and about 400 mg per kg of body weight is suitable in the treatment methods of the present invention. Preferably, from about 0.5 mg to about 150 mg/kg body weight is used as the dosage level where multiple administrations of isocoumarin derivatives are given before the dosage with ionizing radiation and/or chemotherapeutic agent.

[0071] E. Biological Effects

[0072] The following examples are included to demonstrate preferred embodiments of the invention. It should be appreciated by those of skill in the art that the techniques disclosed in the examples which follow represent techniques discovered by the inventors to function well in the practice of the invention, and thus can be considered to constitute preferred modes for its practice. However, those of skill in the art should, in light of the present disclosure, appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the invention.

EXAMPLE 1 Cytotoxicity of NM-3 Toward Tumor Cells

[0073] To determine the extent to which NM-3 [2-(8-hydroxy-6-methoxy-1-oxo-1H-2-benzopyran-3-yl) propionic acid] inhibited the proliferation of, or was cytotoxic toward, human tumor cells and normal mouse cells, a variety of cell lines were grown in the presence of NM-3. The human cell lines used were K562 (leukemia cells), HT29 (colon tumor cells) HT1080 (reticulum blast sarcoma cells), and MCF7 (breast tumor cells). The mouse cells used were NIH3T3 cells (fibroblasts). All cell lines were cultured in 96-well plates to a density of 2-5×10³ cells/well. Culture medium (RPMI 1640 plus 10% FBS) alone or containing NM-3 at one of several concentrations tested was then added to the cultures which were allowed to grow for an additional 3 days. To assess cell growth, 10 μl of WST-1 reagent (a chromogenic substrate for living cells) was added to each well and incubation continued for 3 hrs at 37C. Absorbance at 450 nm was then determined using a plate reader. For each cell type, the IC₅₀ for NM-3 is reported in table 1. Since all IC₅₀s were found to be greater than 100 μg/ml, these results indicated that the in vivo anti-tumor activity of NM-3 did not result from direct inhibition of tumor cell growth. TABLE 1 Cells IC₅₀ μg/ml) K562 250 MKN28  175* PC6 >500   MCF7 223 HT29 >300   HT1080 300 NIH3T3 >100  

EXAMPLE 2 Effects of NM-3 on Ehrlich Solid Tumor Growth

[0074] To determine the antitumor effect of NM-3 on growth of a solid tumor in vivo, 4×10⁶ Ehrlich carcinoma cells per mouse were subcutaneously transplanted into ICR mice (female, 6 weeks old) in the inguinal area. NM-3 was continuously administered via the oral route for 14 days. Tumor weights were then measured on day 15 (Table 2). Whereas tumors from control animals grew to an average size of 1229 mg, tumors from animals treated with 1.25 to 5 mg/kg NM-3 were significantly reduced in size. Tumors from animals receiving the lowest dose of NM-3 (0.63 mg/kg) were also reduced in size but were not significantly different from control values. Thus, NM-3 treatment is associated with a significant reduction in the growth of solid tumors. TABLE 2 Antitumor effect of NM-3 on Ehrlich Carcinoma Dose Schedule Mean Tumor Weight Inhibition t-test^(a)) (mg/kg, p.o.) (days) (mg ± S.D.) (%) (p) 0 — 1229.1 ± 549.7  0.0 — 5 1˜14 589.7 ± 338.3 52.0 <0.05 2.5 ″ 519.5 ± 319.3 57.7 <0.01 1.25 ″ 497.7 ± 265.5 59.5 <0.01 0.63 ″ 822.5 ± 376.2 33.1 n.s.

EXAMPLE 3 Effects of NM-3 on Experimental Tumor Metastasis

[0075] To determine the antitumor effect of NM-3 on metastatic tumor growth, B 16-BL6 melanoma cells (2×10⁴ cells per mouse) were transplanted into BDF1 mice (female, 5 weeks old) via the tail vein. NM-3 was continuously administered via the oral route for 13 days following transplantation of the tumor cells. On day 14, the lungs were excised and fixed, and the metastatic colony numbers were counted. The animals treated with NM-3 (0.08 to 5 mg/kg) experienced a reduction in the number of pleural metastatic foci compared to control animals (Table 3). These results suggest that NM-3 may impart an antitumor effect on the growth of small tumors that arise from tumor metastasis. TABLE 3 Dose Schedule Number of lung metastases Inhibition (mg/kg, p.o.) (days) (Mean ± S.D.) (Range) (%) 0 — 84.2 ± 19.1 (114-51) 0.0 5.0 1˜13 68.4 ± 16.9  (90-47) 18.8 1.25 ″ 72.6 ± 20.6 (106-43) 13.8 0.31 ″ 64.0 ± 23.8 (107-38) 24.0 0.08 ″ 88.7 ± 16.1 (109-62) −5.3

EXAMPLE 4 Effect of NM-3 in Combination Therapy With Cyclophosphamide on Colon 26 Adenocarcinoma

[0076] To determine the effect on tumor growth of NM-3 treatment combined with simultaneous cyclophosphamide treatment, colon 26 adenocarcinoma cells (5×10⁴ cells per mouse) were subcutaneously transplanted into BALB/c mice (female, 7 weeks old) in the inguinal area. NM-3 was continuously orally administered from day 1 to day 72 after the transplantation except on day 14 when cyclophosphamide was dosed. The mean survival days were recorded and reported in Table 4, below. While cyclophosphamide treatment alone resulted in significantly extended survival times (145% of control), NM-3 treatment alone (1 or 5 mg/kg) did not increase survival times. When animals were administered both treatments, survival times significantly increased relative to the control value, and were significantly greater than cyclophosphamide treatment alone in the 5 mg/kg group.

[0077] Thus, these results suggest that NM-3 treatment significantly augments the ability of cyclophosphamide to inhibit tumor growth, which resulted in a concomitant increase survival time. TABLE 4 Cyclophosphamide (300 mg/kg, Dose Schedule Mean Survival Days T/C t-test^(a)) i.v. day 14) NM-3 (mg/kg, p.o.) (day) (days ± S.D.) (%) (p) — — — — 33.0 ± 14.2 100.0 — ± — — — 47.9 ± 13.9 145.1 <0.05 — ± 5 1-13, 15-72 23.5 ± 3.7 71.2 n.s. — ± 1 ″ 33.9 ± 13.6 102.7 n.s. ± ± 5 ″ 55.0 ± 14.7 166.7 <0.01 ± ± 1 ″ 57.8 ± 16.6 175.0 <0.01

EXAMPLE 5 Effect of NM-3 in Combination Therapy with Cyclophosphamide on IMC Carcinoma

[0078] To determine the effect on IMC carcinoma growth of NM-3 treatment combined with simultaneous cyclophosphamide treatment, IMC carcinoma cells (1×10⁶ cells per mouse) were subcutaneously transplanted into CDF1 mice (female, 10 weeks old) in the inguinal area. NM-3 which was dissolved using 5% DMSO+Tween80, was continuously orally administered from day 1 to day 41 after transplantation except on day 14, when cyclophosphamide (300 mg/kg) was injected intravenously. Tumor weights were measured after the excision of tumors on day 42 and are shown in Table 6. Cyclophosphamide treatment alone significantly reduced tumor weight by 70.7%, while NM-3 treatment alone did not significantly reduce tumor weight. Tumor weights were also significantly reduced by the combination treatment of cyclophosphamide and NM-3. In the case of the low dose of NM-3 (1 mg/kg), tumor weight was significantly reduced relative to the tumors from cyclophosphamide-treated animals. Thus, anti-tumor activity of cyclophosphamide could be augmented by NM-3 treatment. TABLE 5 Cyclophosphamide (300 mg/kg, NM-3 Schedule Solid Weight Inhibition t-test^(a)) i.v. day 14) (mg/kg, p.o.) (day) mg ± S.D. (%) (p) — — —   12350 ± 2717.8 0.0 — ± — —  3620.4 ± 1406.3 70.7 <0.01 — 5 1-13, 15-41 10792.4 ± 2979.7 12.6 n.s. — 1 ″ 11,093.0 ± 2040.6  10.2 n.s. ± 5 ″ 2798.3 ± 654.0 77.3 <0.01 ± 1 ″ 2028.9 ± 782.2 83.6*^(b)) <0.01

EXAMPLE 6 NM-3 Increases the Sensitivity of Endothelial Cells to Radiation

[0079] Human umbilical vein endothelial cells (HUVEC) were exposed to a constant amount of gamma radiation in the presence or absence of various concentrations of NM-3 in the culture medium. The numbers of HUVEC colonies that formed following the different treatments were recorded and normalized to the number of colonies formed under control (no NM-3) conditions and the results are shown in FIG. 1. NM-3 treatment decreased HUVEC colony formation is dose dependent manner, with an ED₅₀ of approximately 1 μg/ml (see FIG. 1A). For comparison, HUVEC cells were treated with either angiostatin or endostatin, two additional anti-angiogenic proteins. Neither angiostatin nor endostatin inhibited HUVEC growth to the extent of NM-3 (see FIGS. 1B and 1C).

[0080] In another study of HUVEC radiation sensitivity, cells were treated with NM-3 (100 ng/ml) 1 hr prior to exposure of the cells to increasing doses of gamma irradiation (X-rays). The numbers of HUVEC colonies that formed following the different treatments were recorded and normalized to the number of colonies formed under control conditions (see FIG. 2). Increasing doses of X-rays in the absence of NM-3 decreased HUVEC colony survival to a minimal value of 10% survival at the highest dose tested. In the presence of NM-3, HUVEC colony survival decreased to 0.01% of the initial living cells at the highest X-ray dose. Therefore, NM-3 treatment increased the sensitivity of these cells to X-ray induced lethality by approximately 1000-fold at the highest X-ray dose.

EXAMPLE 7 NM-3 Increases the Radiation Sensitivity of Lewis Lung Carcinoma, In Vivo

[0081] To determine whether NM-3 treatment increases the radiation sensitivity of tumors in vivo, Lewis Lung carcinoma (LLC) tumors were established in C57BL/6 female mice (Frederick Cancer Research Institute) prior to NM-3 and radiation treatment. LLC cells (1×10⁶ cells) were injected in the right hind limb of the mice and tumors were allowed to grow a volume of 250-350 mm³. Tumor volumes were determined by direct measurements with calipers calculated by the formula: V=length×width×depth/2. Mice were then divided into groups and treated with NM-3 (100 mg/kg total) or PBS for two days before beginning radiation therapy. Animals then received NM-3 (25 mg/kg/day, i.p.) or PBS approximately four hours prior to radiation treatment. Tumors were irradiated using a GE Maxitron X-ray generator operating at 150 kV, 30 mA, using a 1 mm aluminum filter at a dose rate of 188 cGy/minute. Mice were shielded with lead except for the tumor-bearing area in the hind limb. Treatments and tumor measurements continued for a period of 17 days (see FIG. 4). X-ray treatment alone resulted in a highly significant delay in tumor growth. Whereas control tumors reached 8 initial tumor volumes (Vo) after 8 days, X-ray treated tumors required 16 days to grow to this size. When NM-3 treatment was added to the radiotherapy, further tumor growth was markedly reduced and only began to appear after 15 days. This result was not due to a direct antitumor effect of NM-3 because NM-3 alone did not inhibit tumor growth at all. These results, as shown in FIG. 3A, indicate that NM-3 treatment dramatically enhances the sensitivity of internally growing tumors to subsequent radiation therapy. For comparison, data are plotted with two additional anti-angiogenic drugs, antiostatin and endostatin (see FIGS. 3B and 3C). Angiostatin showed some radiation sensitization, whereas endostatin did not.

[0082] In a second similar experiment, X-ray treatment and X-ray treatment combined with NM-3 treatment were again compared for their relative abilities to inhibit LLC tumor growth. However, the treatment period was extended to determine whether either treatment regimen was able to initiate complete tumor cures. Animals were injected with 106 cells initially and starting tumor volumes were approximately 500 mm³. Tumors were irradiated on days 2 and 4 with 20 Gy X-irradiation. NM-3 was administered at 25 μg/kg daily over the first four days. The tumors of both groups increased slightly in size following initiation of treatment and then began to decrease after several days. Tumors in the X-ray only group began to increase steadily in size after the 10^(th) day of continuous treatment. In contrast, tumors in the NM-3+X-ray group continued to decrease in size following the initial growth phase. Ultimately, 9 of 10 animals receiving NM-3+X-ray treatment experienced a complete cure while only 3 of 10 animals were cured by the X-ray treatment alone.

[0083] In summation, these results demonstrate that NM-3 holds significant therapeutic promise as a radiation sensitizing agent. In vitro experiments document the enhanced sensitivity of endothelial cells to radiation as a result of NM-3 exposure and suggest a rationale for treating human tumors. The in vivo tumor studies show that this strategy of preventing tumor growth can be an effective treatment.

EXAMPLE 8 In Vivo Study Designed to Evaluate Antitumor Activity of NM-3 in Combination With Paclitaxel Against the MDAMB-435 Human Breast Orthotopic Model in Nude Mice

[0084] In order to determine the effect of the combination of NM-3 with the cytotoxic drug, paclitaxel on human breast tumor xenografts, female NCRNU nude mice were implanted with MDAMB-435 cells into the subaxillary mammary fat pad. NM-3 was administered via intraperitoneal (i.p.) injection daily at doses ranging from 10-100 mg/kg; paclitaxel was administered via i.p. injection every 7 days, starting on day 0, at 10 mg/kg.

[0085] As a single agent, paclitaxel showed minimal effect at 10 mg/kg, given every 7 days via i.p. injection, whereas 20 mg/kg had a significant effect on tumor growth inhibition. FIG. 4 shows mean tumor volumes plotted against time, and the results of this study are summarized in Table 6, below. NM-3 administered as a single agent at 100 mg/kg; i.p. daily resulted in a tumor growth inhibition (TGI) of 15.29%. The addition of paclitaxel at 10 mg/kg q7d resulted in a TGI of 72.35%. There were 5 complete responses. Paclitaxel alone or in combination with NM-3 at the lower dose of 10 mg/kg; i.p. daily resulted in no tumor growth inhibition. No substantial weight loss was observed in any of the groups throughout the protocol. TABLE 6 % Tumor Mice with NM-3 (mg/kg; Final Tumor Wt. Growth Complete Taxol I.P. daily) n (mg) +/− SEM Inhibition Shrinkage t-test (p) 0 0 9 212.5 ± 30.92 — 0 — 10 mg/kg q7d 10 9 228.8 ± 26.35 — 0 — 10 mg/kg q7d 100 9 58.75 ± 29.91 72.35 5 <0.005 100 9 180.0 ± 18.13 15.29 0 n.s. 10 mg/kg q7d 0 9 215.6 ± 19.73 — 0 —

[0086] In a second study, treatment was initiated when tumor volumes reached 100 mm³. Paclitaxel was administered at the fixed dose of 12.5 mg/kg, q7d and NM-3 was dosed at 10 and 100 mg/kg, i.p. daily for 28 days. FIG. 5 shows mean tumor volume ratios plotted against time. The results of this study are summarized in Table 7, below. NM-3 alone given at a daily dose of 10 mg/kg had no significant tumor growth inhibition, whereas at NM-3 at 100 mg/kg resulted in a TGI of 26.67%. Paclitaxel administered alone at 12.5 mg/kg, q7d resulted in a TGI of 26.52%, and when combined with NM-3, the TGI was 46.10%. All treatments were well tolerated, with no substantial weight loss being observed. TABLE 7 % Tumor Mice with NM-3 (mg/kg, Final Tumor Ratio Growth Complete Taxol I.P. daily) n (V/Vo) +/− SEM Inhibition Shrinkage t-test (p) 0 0 9 6.41 ± 0.40 — 0 12.5 mg/kg q7d 10 9 4.99 ± 0.66 22.15 0 n.s. 12.5 mg/kg q7d 100 9 3.45 ± 0.54 46.10 0  <0.001 100 9 4.70 ± 0.56 26.67 0 <0.03 12.5 mg/kg q7d 0 9 4.71 ± 0.76 26.52 0 <0.03

[0087] A comparison was also made between different delivery routes of NM-3 in the combination studies. NM-3 given i.p. daily, bid, and continuously using Alzet mini osmotic pumps in combination with paclitaxel was evaluated for effectiveness in reducing tumor growth. FIG. 6 shows mean tumor volume ratios plotted over time, and Table 8, below, summarizes the data. Bid dosing with NM-3 was more effective than daily dosing, when combined with paclitaxel. However, continuous delivery using mini-pumps implanted subcutaneously was not as effective as i.p. delivery. TABLE 8 % Tumor NM-3 Final Tumor Ratio Growth Taxol (mg/kg) Route n (V/Vo +/− SEM Inhibition t-test (p) 0 0 9 6.41 ± 0.40 — 12.5 mg/kg q7d 100 i.p. daily 9 3.45 ± 0.54 46.10 <0.001 12.5 mg/kg q7d 100 i.p. bid 9 3.172 ± 0.629 50.52 <0.001 12.5 mg/kg q7d 100 Continuous 9 4.386 ± 1.157 31.58 n.s.

EXAMPLE 9 Antitumor Activity of NM-3 in Combination With 5-Fluorouracil vs. MDAMB-435 Human Breast Orthotopic Model in Nude Mice

[0088] In order to evaluate the antitumor activity of NM-3 in combination with 5-Fluorouracil (5-FU) vs. MDAMB-435 human breast tumor xenografts, female NCRNU nude mice were implanted with MDAMB-435 cells into the subaxillary mammary fat pad. When the tumors were between 50 and 80 mm³, NM-3 was administered via intraperitoneal (i.p.) injection daily at 10 and 100 mg/kg; 5-FU was administered via i.p. injection on days 0 and 14, at 10 mg/kg. Mice were weighed twice weekly, and tumor measurements were taken by calipers twice weekly. Mice were euthenized at the end of the treatment period. Upon termination, the mice were weighed, sacrificed and their tumors were excised. The mean tumor weight per group was calculated, and the mean treated tumor weight/mean control tumor weight×100% was subtracted from 100% to give the tumor growth inhibition (TGI) for each group.

[0089] Initial studies were conducted with 5-Fu to determine the optimal dose of this agent when administered in combination with NM-3. When 5-FU was administered at 10 mg/kg, q14d, there was no significant TGI. Animals treated with NM-3 administered as a single agent at 100 mg/kg; i.p. daily had a final mean tumor weight not significantly different than the control group. 5-Fu in combination with NM-3 at the dose of 100 mg/kg; i.p. daily resulted in a TGI of 50.80%. FIG. 7 shows mean tumor volume ratios plotted over time, and Table 9, below, summarizes the data. No substantial weight loss was observed in any of the groups throughout the protocol. TABLE 9 NM-3 Final Tumor % Tumor (mg/ Wt. Growth t-test 5-FU kg/day) n (mg) +/− SEM Inhibition (p) 0 0 9 341.5 ± 28.70 0 — 10 mpk q14d; 0,14 10 9 257.3 ± 31.06 24.66 0.08 10 mpk q14d; 0,14 100 9 168.0 ± 45.6  50.80 0.01 0 100 9 259.2 ± 46.99 24.1 0.17 10 mpk q14d; 0,14 0 9 259.6 ± 36.22 23.98 0.12

EXAMPLE 10 NM-3 Enhances the Ability of Ionizing Radiation (IR) to Inhibit the Growth of Tumors In Vivo

[0090] The effects of NM-3 and IR on tumor growth were assessed in Lewis Lung Carcinoma (LLC), Seg-1, and SQ-20B tumors implanted in C57BL/6 nude mice.

[0091] By day 7, LLC tumors in the control group and the NM-3 group grew to 8.02±1.24 and 6.19±0.44 times original volume, respectively. Animals in these treatment groups were sacrificed on day 7 due to tumor burden. LLC tumors in the IR (20+20 Gy) group initially grew and then regressed to 1.06±0.08 times original volume (day 7). Regression was followed by regrowth to 2.98±0.83 times original volume at day 15 when the experiment was terminated. Combined treatment with NM-3 and IR significantly reduced mean tumor volume when compared with IR alone at day 3, 4, 5, 9, 11, 13 and 15. (FIG. 8A) Seg-1 tumors in the control group and the NM-3-treated group grew to 6.30±0.42 and 6.74±0.62 times original volume by day 15 at which time the animals were sacrificed due to tumor burden. Tumors in the IR (4 doses of 5 Gy) group initially regressed (0.64±0.03 times original volume, day 7) and then regrew (1.83+0.11, day 15). Combined treatment with NM-3 and IR significantly reduced mean tumor volume at days 15, 17, 19, 21 and 23 when compared with IR treatment alone. (FIG. 8B). The combined treatment group demonstrated a growth delay of 14 days compared to the control group and 3 days compared to IR alone group.

[0092] In experiments conducted using SQ-20B tumors, control tumors grew to 5.2±0.94 times original volume by day 20. A similar pattern of tumor growth was observed in the NM-3 alone treatment group (4.3±1.03, day 20). Animals in these two groups were subsequently sacrificed because of tumor burden. Tumors in the IR treatment group (65 Gy) doubled in size by day 6, and regressed to 50% of original volume at day 23. By day 38, IR treated tumors regrew to twice original volume. Animals treated with NM-3 and IR doubled in size by day 6 and then regressed to 77% of original volume at day 23. Unlike the tumors treated with IR alone, tumors receiving combined therapy with NM-3 and IR failed to reach original volume by day 38 (p=0.006, t-test).

[0093] NM-3 increased the antitumor effects of IR in three different tumor model systems, both murine and human, as measured by tumor regression. 

1. A method for inhibiting the growth of an endothelial cell comprising a contacting said endothelial cell with an isocoumarin derivative of the formula:

wherein each of X¹, X² and X³ is independently sulfur or oxygen; X⁴ is sulfur, oxygen or an —NH— group; R¹ is hydrogen or C₁₋₆ alkyl; and R² and R³ may be the same or different and each represents C₁₋₆ alkyl, and C₇₋₁₀ alkaryl, hydroxy or hydrogen; and n is zero on a whole integer of 1 to 3; and (b) further contacting said tumor cell with a chemotherapeutic agent, wherein said dose of isocoumarin derivative, when combined with said dose chemotherapeutic agent is effective to inhibit the growth of said endothelial cell in an enhanced effect relative to administration of said isocoumarin derivative or said chemotherapeutic agent alone.
 2. The method of claim 1, wherein the isocoumarin derivative comprises a compound of the formula given in claim 1, wherein X¹, X² and X³ each are oxygen; X⁴ is oxygen or sulfur; R¹ is C₁₋₃ alkyl; R² and R³ are each independently selected from hydrogen and C₁₋₆ alkyl and n is 0, 1 or
 2. The method of claim 2, wherein the isocoumarin derivative has the formula:

wherein R¹ is C₁₋₃ alkyl and R² and R³ each represents hydrogen or C₁₋₆ alkyl and n is 0 or
 1. 3. The method of claim 1, wherein the tumor cell is contacted with the isocoumarin derivative and a chemotherapeutic agent selected from a Tubulin interactive or a DNA-interactive agent or an antimetabolite.
 4. The method of claim 3, wherein the chemotherapeutic agent is a Tubulin interactive agent.
 5. The method of claim 4, wherein the Tubulin interactive agent is a Paclitaxel.
 6. The method of claim 3, wherein the chemotherapeutic agent is a DNA-interactive agent.
 7. The method of claim 6, wherein the DNA-interactive agent is cyclophosphamide.
 8. The method of claim 3, wherein the chemotherapeutic agent is an antimetabolite.
 9. The method of claim 8, wherein the antimetabolite is 5-fluorouracil.
 10. A method for treating cancer in a human patient comprising administering an isocoumarin derivative of the formula given in claim 1 to said human patient and administering a chemotherapeutic agent as a second treatment modality, wherein said cancer is sensitive to the administration of said isocoumarin derivative when combined with the second treatment modality, and wherein such administration effects an enhanced treatment of said cancer relative to either said isocoumarin derivative or said shemotheraputic agent as a single modality.
 11. The method of claim 10, wherein the isocoumarin derivative comprises a compound of the formula given in claim 1, wherein X¹, X² and X³ each are oxygen; X⁴ is oxygen or sulfur, R¹ is C₁₋₃ alkyl; and R² and R³ are each dependently selected from hydrogen and C₁₋₆ alkyl.
 12. The method of claim 11, wherein the isocoumarin derivative has the formula:

wherein R¹ is C₁₋₃ alkyl and R² and R³ each represents hydrogen or C₁₋₆ alkyl and n is 0 or
 1. 13. The method of claim 10, wherein the chemotherapeutic agent is selected from a Tubulin interactive agent, a DNA-interactive agent, and an antimetabolite.
 14. The method of claim 13, wherein the chemotherapeutic agent is a Tubulin interactive agent.
 15. The method of claim 14, wherein the Tubulin interactive agent is a Paclitaxel.
 16. The method of claim 10, wherein the chemotherapeutic agent is a DNA-interactive agent.
 17. The method of claim 16, wherein the DNA-interactive agent is cyclophosphamide.
 18. The method of claim 10, wherein the chemotherapeutic agent is an antimetabolite.
 19. The method of claim 18, wherein the antimetabolite is 5-fluorouracil. 20 The method of claim 10, wherein said tumor is selected from the group consisting of skin cancer, prostate cancer, lung cancer, brain cancer cell, breast cancer, ovarian cancer, cervical cancer, liver cancer, pancreatic cancer, colon cancer, stomach cancer and leukemia. 